灯盏乙素和灯盏花素对急性心肌梗死的保护作用

目的研究灯盏乙素和灯盏花素对急性心肌梗死的保护作用。方法建立大鼠急性心肌梗死模型后,腹腔注射不同剂量灯盏乙素和灯盏花素,4h后取出心脏行氯化硝基四氮唑蓝（NBT）染色,测量心肌梗死面积,比较两种药物对心肌梗死面积影响的量效关系;建立犬急性心肌梗死模型,股静脉注射50mg/kg灯盏花素或灯盏乙素,记录不同时间点的心外膜电图,比较两种药物对心肌缺血程度和范围的影响。结果灯盏乙素单体能够降低心肌梗死面积,抑制梗死区心肌细胞的凋亡,50mg/kg灯盏乙素能够降低左冠状动脉前降支结扎后犬心外膜电图抬高的∑ST段。结论灯盏乙素单体是灯盏花素的主要药理活性成分,较灯盏花素具有更好的量效关系。     

The long-lasting anti-anginal effects of CP-060S in a rat model of arginine vasopressin-induced myocardial ischaemia

The anti-anginal effect of CP-060S, a new cardioprotective agent that prevents myocardial Na+-, Ca2+-overload and has Ca2+-channel blocking activity, was evaluated in a rat model of arginine8-vasopressin (AVP)-induced cardiac ischaemia. Infusion of AVP (0.2 IU kg(-1)) depressed the electrocardiogram (ECG) ST segment, an index of myocardial ischaemia. Vehicle, CP-060S and diltiazem were given orally 1, 2, 4, 8, 12 and 24 h before the administration of AVP. CP-060S, at 3 mg kg(-1) and 10 mg kg(-1), suppressed AVP-induced ST-segment depression for 2 h and 12 h, respectively. In contrast, diltiazem, at 10 and 30 mg kg(-1), suppressed AVP-induced ST-segment depression for only 1 h. The persistent suppression of the AVP-induced ST-segment depression by CP-060S correlated with the time course of changes in its plasma concentration. The minimum effective concentration of CP-060S was estimated to be 30 ng mL(-1) (approximately 50 nM), consistent with its vasorelaxant potency in rat isolated aortic strips (concentration producing 50% relaxation of KCl contraction, IC50 = 32.6+/-8.3 nM). Intravenously administered CP-060S, at 300 microg kg(-1) and diltiazem at 500 microg kg(-1) showed similar haemodynamic changes, whereas CP-060S, at 300 microg kg(-1), significantly suppressed AVP-induced ST-segment depression and diltiazem, at 500 microg kg(-1), had no effect on AVP-induced ST-segment depression. In summary, orally administered CP-060S exerted a long-lasting anti-anginal effect proportionate to the time course of changes in its plasma concentration in a rat model of AVP-induced ischaemia.     

The anti-ischemic effects of CP-060S during pacing-induced ischemia in anesthetized dogs

CP-060 S, (-)-( S)-2-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-3-[3-[N-methyl-N-[2-(3 ,4-methylenedioxyphenoxy)ethyl]-amino]propyl]-1,3-thiazolidin++ +-4-one hydrogen fumarate, is a novel cardioprotective drug which prevents Na+-, Ca2+-overload and has Ca2+ channel blocking activity. We compared the anti-ischemic effects of CP-060S with those of diltiazem, a Ca2+ channel blocker, and R56865, N-[1-[4-(4-fluorophenoxy)butyl]-4-piperidinyl]-N-methyl-2-benzothiazo lamine, a Na+-, Ca2+-overload inhibitor, in a canine pacing-induced ischemia model. CP-060S 100 microg kg(-1) significantly suppressed the pacing-induced ischemic epicardial ST-segment elevation by maximally 75%, while diltiazem 100 microg kg(-1) suppressed it by maximally 35%. R56865 100 microg kg(-1) significantly suppressed the ST-segment elevation by maximally 30%. In addition, diltiazem 100 microg kg(-1) caused synergistic suppression of ST-segment elevation by 70% when administered simultaneously with R56865 100 microg kg(-1). These results suggest that a Na+-, Ca2+-overload preventive action and a Ca2+ channel blocking action independently contribute to the suppression of the ST-segment elevation. Therefore, CP-060S may suppress pacing-induced ST-segment elevation by a dual action by preventing Na+-, Ca2+-overload and the Ca2+ channel blockade.     

Astragaloside IV improved intracellular calcium handling in hypoxia-reoxygenated cardiomyocytes via the sarcoplasmic reticulum Ca-ATPase

Although astragaloside IV, a saponin isolated from Astragalus membranaceus, has been shown to protect the myocardium against ischemia/reperfusion injury, its effect on the status of sarcoplasmic reticulum (SR) Ca2+ transport in the injured myocardium remains largely unknown. In this study, we investigated whether in cultured cardiomyocytes subjected to hypoxia and reoxygenation (H/R) administration of astragaloside IV during H/R attenuates the myocardial cell injury and prevents changes in Ca2+ handling activities and gene expression of SR Ca2+ pump. Cultured cardiomyocytes from neonatal rats were exposed to 6 h of hypoxia followed by 3 h of reoxygenation. Myocyte injury was determined by the release of cardiac troponin I in supernatant. Astragaloside IV significantly inhibited cardiac troponin I release after H/R in a dose-dependent manner. The diastolic [Ca2+]i measured with Fura-2/AM was significantly increased after reoxygenation. Astragaloside IV prevented the rise of diastolic [Ca2+]i and the depression of caffeine-induced Ca2+ transients caused by H/R. Furthermore, the observed depressions in SR Ca2+-ATPase activity as well as the mRNA and protein expression of SR Ca2+-ATPase in hypoxic-reoxygenated cardiomyocytes were attenuated by astragaloside IV treatment. These results suggest that the beneficial effect of astragaloside IV in H/R-induced injury may be related to normalization of SR Ca2+ pump expression and, thus, may prevent the depression in SR Ca2+ handling.     

玉郎伞两种黄酮单体对心肌细胞缺氧/复氧损伤的保护作用

目的研究从玉郎伞(Yulangsan,YLS)中首次分离的两种黄酮单体对体外培养大鼠乳鼠心肌细胞缺氧/复氧损伤的保护作用,并初步探讨其作用机制。方法建立体外培养大鼠乳鼠心肌细胞缺氧/复氧损伤模型,倒置显微镜下观察加入YLS两种单体的含药血清(10%、5%、2.5%)后,各组缺氧/复氧心肌细胞形态学和搏动频率的变化;以MTT法检测各组细胞的存活率;用ELISA法测定心肌细胞Na+,K+-ATP酶、Ca2+,Mg2+-ATP酶活性及细胞培养上清液中总超氧化物歧化酶(T-SOD)、乳酸脱氢酶(LDH)、一氧化氮合酶(NOS)活性和丙二醛(MDA)含量。结果与模型组相比,YLS两种单体含药血清的高、中剂量均能明显增加心肌细胞的存活率,增强Na+,K+-ATP酶、Ca2+,Mg2+-ATP酶活性,降低细胞培养上清液LDH、NOS活性、MDA含量,提高T-SOD活性并呈剂量依赖性(P<0.05)。结论两种YLS单体对体外培养大鼠乳鼠心肌细胞缺氧/复氧损伤具有保护作用,其机制可能与清除自由基、抑制心肌细胞Ca2+超载有关。     

Calcium channel blockade limits transcriptional,translational and functional up-regulation of the cardiac calpain system after myocardial infarction

Abnormal Ca(2+) inward current through cardiac Ca(2+) channels during ischemia has been shown to be an initial signal for activation of myocardial Ca(2+)-dependent enzymes. This study investigated the contribution of cardiac L- and T-type Ca(2+) channels in the calpain-mediated myocardial damage following myocardial infarction. Myocardial infarction was induced by permanent ligation of the left coronary artery. Infarcted rats were orally treated with placebo, amlodipine (L-channel blockade; 4 mg/kg/day) or mibefradil (L-/T-channel blockade; 10 mg/kg/day) beginning 7 days before induction of myocardial infarction. Gene expression, protein levels and enzyme activity of calpains I and II were measured 1, 3, 7 and 14 days postcoronary occlusion in the noninfarcted and infarcted myocardium. Infarct size, left ventricular dilation and interstitial collagen volume fraction were determined in picrosirius red-stained hearts. Myocardial infarction induced an up-regulation of calpain I mRNA, protein and activity in the noninfarcted myocardium (maximum 14 days postinfarction), whereas mRNA, protein and activity of calpain II were maximally increased in the infarcted myocardium 3 days postinfarction. Fourteen days postinfarction, infarct size was 49%, the left ventricle was dilated and interstitial collagen volume fraction was increased. Amlodipine-inhibited mRNA, protein and activity up-regulation of calpain I decreased interstitial collagen volume fraction and infarct size. Mibefradil-attenuated mRNA, protein and activity up-regulation of calpain II at all four time points measured and of calpain I at 7 and 14 days postinfarction reduced infarct size and prevented left ventricular dilation. Infarction-induced cardiac hypertrophy was accompanied by an up-regulation of calpain I, whereas calpain II was up-regulated in the infarcted myocardium. Cardiac L- and T-type Ca(2+) channel blockade differentially reduced postinfarction remodeling associated with selective inhibition of cardiac calpains I and II, respectively.     

Protective effects of scutellarin and breviscapine on brain and heart ischemia in rats

Scutellarin is an active molecule existing in Erigeron breviscapus (vant.) Hand-Mazz. The present work was designed to study the antiischemic effects of scutellarin and its mixture with another substance, breviscapine, in male Sprague-Dawley (SD) rats. Ligature of left anterior descending arteries was performed to induce acute myocardial infarction (MI), and the middle cerebral artery occlusion was created to induce focal cerebral ischemia. The MI size was significantly reduced by scutellarin (15 and 50 mg/kg) but not by breviscapine (5 to 50 mg/kg); the effect of scutellarin on the anti-MI was dose-dependent. Compared with control group, scutellarin (50 mg/kg) reduced the myocardium cell apoptosis in MI rats. The two drugs together (5 to 50 mg/kg) significantly reduced infarction size in focal brain ischemic rats (P < 0.05). There were no significant differences among the 3 dosages in breviscapine-treated rats, and the effect of scutellarin on the anticerebral ischemia was dose-dependent. The results demonstrate that the protective effects of scutellarin on cardiovascular and cerebrovascular ischemia were better than its mixture, breviscapine, in rats.     

Comparative analysis of antiarrhythmic and proarrhythmogenic effects of drugs for neuroleptanalgesia, ataralgesia, and antidepranalgesia in experimental acute myocardial infarction

Proarrhythmogenic and antiarrhythmic effects of drugs for neuroleptanalgesia (NLA), ataralgesic (ATA) and antidepranalgesia (ADA) in chronic experiments on sleepless rabbits with acute myocardial infarction, with and without tachyarrhythmias, were studied using ECG, intraventricular electromanometry and tetropolar rheography. NLA (phentanylum, 1 microg/kg + droperidol, 5 microg/kg), ADA (pyrazidole, 1 mg/kg + tramal, 1 mg/kg) and ATA (diazepam, 1 mg/kg + promedol 0.5 mg/kg) produce antiarrhythmic effect with maximum manifestation of NLA on the 3rd day, and of ATA and ADA on 3-5th day. This medication increased blood supply and contractility of ischemic myocardium. Proarrhythmogenic effects of this medication were not observed.     

Urantide对心肌缺血性损伤的保护作用

研究UT受体拮抗剂——urantide对心肌缺血性损伤的保护作用及其机制。小鼠心肌缺血采用皮下注射(sc)异丙肾上腺素(Iso)法，观察心电图ST段的变化，测定小鼠血清中乳酸脱氢酶(LDH)、一氧化氮合酶(NOS)的活性以及丙二醛(MDA)、一氧化氮(NO)的含量， HE染色观察心肌组织病理损伤情况。建立乳鼠原代心肌细胞缺氧再给氧模型，采用ELISA法观察urantide对细胞培养上清液中肌钙蛋白I(cTnI)的影响，比色法测LDH活性；MTT法观察细胞存活率及激光共聚焦检测细胞内钙离子浓度的变化。实验揭示urantide (3～30 μg·kg^-1)可明显抑制小鼠心电图ST段的抬高； urantide (10及30 μg·kg^-1)可显著降低小鼠血清中LDH活性和MDA含量，明显升高NOS活性和NO含量，同时减轻异丙肾上腺素诱导的心肌病理损伤。在乳鼠原代心肌细胞缺氧再给氧模型中， urantide (1×10^-6和1×10^-7 mol·L^-1)能明显增加细胞存活率，降低培养上清液中LDH的活性； urantide (1×10^-6～1×10^-9 mol·L^-1)能显著降低细胞培养上清液中cTnI的增高和细胞内钙离子浓度的上升。上述结果表明， urantide对心肌缺血及缺氧再给氧所致心肌细胞的损伤具有一定的保护作用，其作用机制可能与增加NOS活性、促进NO合成及抑制钙超载有关。     

The protein kinase inhibitor fasudil protects against ischemic myocardial injury induced by endothelin-1 in the rabbit

Endothelin-1 (ET-1) induces severe pathologic conditions such as coronary spasm followed by vasospastic angina pectoris and acute myocardial infarction. The related pathophysiologic mechanisms have remained obscure. Endothelin-1 receptor (ET(A) and ET(B)) is reported to couple with several types of G protein-involved pathways that participate in phospholipase C activation and atrial myofibrils organization into sarcomeric units. Here we demonstrate that ET-1 induces histologic and pathologic dysfunction in the rabbit myocardium and that such pathologic events are prevented by the Rho-kinase inhibitor fasudil. Although the bolus injection of ET-1 (1.4 nmol/kg) via the auricular vein of the rabbit induced only transient T-wave elevation, irreversible, severe histologic changes were observed in papillary muscles of the ventricle, and multifocal myocardial necrosis with infiltration of neutrophils and macrophages in the left ventricle occurred. Oral administration of fasudil (10 mg/kg) significantly reduced the occurrence of myocardial injury determinants, whereas conventional Ca2+ channel blockers (nifedipine, diltiazem) and a K+ channel opener (nicorandil; 10 mg/kg, p.o. each) showed a lesser or no effect on such determinants. These results suggest that ET-1 induces severe myocardial dysfunction based not only on the occurrence of vasospastic ischemia but also on its direct effects on the myocardium.     

硝酸甘油与丁丙诺啡合用抗大鼠心肌缺血的药理性预适应研究

目的　研究硝酸甘油 (nitroglycerin ,NG)和丁丙诺啡(buprenorphine ,BU)两药单用及合用抗心肌缺血的药理性预适应的延迟相保护作用。方法　♂大鼠分为 5组 ,Sham组静注等容积NS ,DIP组行肠系膜上动脉结扎 10min处理 ,BU组静注盐酸丁丙诺啡 1 0mg·kg- 1,NG组静注NG 0 3mg·kg- 1,B +N组分别给上述剂量BU和NG。 2 4h后各组行 3 0min冠脉结扎缺血 /2h再灌。各组均于术后 15min、缺血期和再灌期连续监测心率、血压、ST 段和心律失常情况 ;测定缺血 3 0min和再灌 2h血浆LDH、CK ;再灌 2h后行HE染色与TTC染色定性和定量测定心肌坏死情况。结果　与Sham组比较 ,DIP组可降低心脏缺血期ST段抬高幅度 (P <0 0 1) ,推迟VPC出现时间 ,缩短持续时间 (P <0 0 5) ,降低二联律发生率 ,降低缺血期血浆LDH水平 (P <0 0 5) ,缩小心肌坏死面积 (P <0 0 5)。BU组可降低心脏缺血期ST段抬高幅度 (P <0 0 1) ,推迟VPC出现时间 ,缩短持续时间 (P <0 0 5) ,降低二联律和室颤的发生率 (P <0 0 5) ,降低缺血期血浆LDH水平 ,缩小心肌坏死面积 (P <0 0 5)。NG组可降低ST段抬高幅度 (P <0 0 1) ,缩短VPC持续时间 (P <0 0 1) ,降低二联律、室速和室颤的发生率 (P<0 0 1) ,明显缩小心肌坏死面积 (P <0 0 1) ,减轻心肌坏死?     

Metoprolol attenuates postischemic depressed myocardial function in papillary muscles isolated from normal and postinfarction rat hearts.

The present study was designed to test the hypothesis that metoprolol treatment may enhance tolerance to ischemia in normal and postinfarction rat myocardium. Myocardial infarction was induced by permanent ligation of the left coronary artery in adult rats. Animals were divided into sham-operated and infarction groups with or without metoprolol treatment. Metoprolol treatment (60 mg/kg/day via gastric gavage) was started on the second day after surgery and continued until sacrifice at 6 weeks after myocardial infarction. Isometric force and intracellular Ca(2+) ([Ca(2+)](i)) transients were simultaneously recorded in isolated left ventricular papillary muscles. Ischemia was simulated by immersing the muscles into fluorocarbon with hypoxia. Metoprolol treatment induced a significant improvement of isometric force and ameliorated diastolic [Ca(2+)](i) overload in postinfarction rat myocardium at baseline. Metoprolol treatment also reduced diastolic [Ca(2+)](i), ameliorated the depression of developed tension during ischemia, and enhanced recovery of postischemic depressed myocardial function in sham-operated and postinfarction rat papillary muscles. Protein levels of the sarcoplasmic reticulum Ca(2+) ATPase of left ventricles and postischemic papillary muscles from metoprolol-treated rats were higher than those in placebo-treated animals. We concluded, therefore, that metoprolol treatment produced appreciable improvement of intracellular Ca(2+) handling during ischemia-reoxygenation cycles, and enhanced recovery of postischemic depressed myocardial function in both normal and postinfarction rat myocardium.     

The effects of propranolol and acebutolol on left ventricular function and coronary haemodynamics in the conscious dog with myocardial ischaemia.

1 The cardiovascular effects of the beta-adrenoceptor blocking drugs, propranolol and acebutolol, on regional coronary blood flow and left ventricular function have been investigated in the conscious dog with developing myocardial infarction. 2 Propranolol (1 to 1.5 mg/kg) or acebutolol (4 to 5 mg/kg) were administered intravenously 2 to 3 h after occlusion of the left anterior descending coronary artery. 3 Propranolol or acebutolol administration resulted in a relative increase in flow to the ischaemic area of the myocardium, particularly to the subendocardium. 4 Propranolol produced a greater reduction in heart rate and myocardial contractility than acebutolol. 5 These results demonstrate that beta-adrenoceptor blocking drugs reduce myocardial oxygen consumption and increase coronary flow to the ischaemic area of the myocardium after coronary artery occlusion in the conscious dog.     

Maitotoxin-induced myocardial cell injury: calcium accumulation followed by ATP depletion precedes cell death

Maitotoxin, the most potent marine toxin, is known to increase the uptake and the accumulation of Ca2+ into cells, and was used in the present study to investigate the mechanisms of myocardial cell damage induced by Ca2+ overload. In cultured cardiomyocytes, isolated from 2-day-old rats, maitotoxin affected cell viability, as indicated by the leakage of the cytosolic enzyme lactate dehydrogenase (LDH) and of radiolabeled adenine nucleotides into the extracellular medium. Maitotoxin-induced leakage of LDH steadily increased between 30 min and 24 hr, and was preceded by a marked depletion of intracellular ATP. Addition of maitotoxin resulted in a rapid influx of extracellular Ca2+, as detected by preincubating the cells in the presence of 45Ca; this effect evolved in a few minutes, thus preceding the signs of cell death. Cytosolic levels of free Ca2+ ([Ca2+]i) were monitored by loading freshly isolated, suspended cardiomyocytes with the intracellular fluorescent probe fura-2; in these cells, maitotoxin induced a dose-dependent increase in [Ca2+]i, with a lag phase of less than a minute. All these effects of maitotoxin were inhibited by reducing Ca2+ concentration in the culture medium or by incubating the cells with the calcium-channel blocking drug verapamil. It is thus demonstrated that maitotoxin-induced cardiotoxicity is secondary to an inordinate influx of Ca2+ into the cells. It is also suggested that, in those conditions that lead to an inordinate accumulation of Ca2+ into myocardial cells, the unmatched demands of energy and the depletion of ATP play a primary role in the irreversible stage of cell damage.     

Effect of SMP-300, a new Na+/H+ exchange inhibitor, on myocardial ischemia and experimental angina models in rats

We evaluated the effects of SMP-300 (N-(aminoiminomethyl)-11-chloro-5,6,7,8-tetrahydro-8-oxo-4H-pyrrolo[3,2,1-kl][1]benzazocine-2-carboxamide monomethanesulfonate monohydrate), a newly synthesized compound, on Na+/H+ exchange activity in rat cardiomyocytes and on other ion transporters, channels and receptors. We also investigated the protective effects of SMP-300 in isolated ischemic rat hearts and rat isoproterenol- or vasopressin-induced experimental angina models. SMP-300 concentration-dependently inhibited recovery from acidosis in rat myocytes, and its IC50 for Na+/H+ exchange was 6 nM. In comparison, its IC50s for Na+/Ca2+ exchange and for the Na+ channel were >1000 nM, and those for other channels or receptors tested were >10,000 nM. In rat isolated perfused hearts, SMP-300 (10(-8)-10(-7) M), administered only at preischemia and not during reperfusion, significantly improved the postischemic recovery of cardiac function. SMP-300 (0.03-0.3 mg/kg, i.v.) or 5-(N-ethyl-N-isopropyl)-amiloride (1 mg/kg, i.v.) prevented the isoproterenol-induced ST-segment depression in the ECG of anesthetized rats, in a dose-dependent manner. SMP-300 (0.1 mg/kg, i.v.) and 5-(N-ethyl-N-isopropyl)-amiloride (1 mg/kg, i.v.) also inhibited the vasopressin-induced ST-segment depression in the ECG of anesthetized rats. This is the first report presenting the protective effect of Na+/H+ exchange inhibitors on isoproterenol- or vasopressin-induced ECG changes in rats, providing the future perspective of SMP-300, a potent Na+/H+ exchange inhibitor, as an anti-anginal drug.     

黄芩苷对大鼠心肌缺血再灌注损伤的保护作用(英文)

目的：研究中药有效成分黄芩苷(baicalin)对大鼠心肌缺血再灌注损伤的作用及其机制。方法：雄性Wistar大鼠随机分为4组,假手术组、对照组和黄芩苷50,100 mg·kg~(-1)组。结扎大鼠左冠状动脉前降支30 min后松开结扎线120 min复制心肌缺血-再灌注损伤模型,以多道生理记录仪持续记录左室压力变化速率(±dp/ dt_(max))和左室舒张末期压(LVEDP)的变化。检测心肌丙二醛(MDA)含量、超氧化物歧化酶(SOD)、Na~+-K~+-ATP酶和Ca~(2+)-ATP酶活性以及血清乳酸脱氢酶(LDH)和磷酸肌酸激酶(CK)含量,以透射电镜观察心肌超微结构的改变。结果：与假手术组比较,对照组大鼠左室±dp/dt_(max)明显降低(P＜0.01),而LVEDP明显升高(P＜0.01)。静脉注射黄芩苷50,100 mg·kg~(-1)可使降低的±dp/dt_(max)明显升高(P＜0.05,P＜0.01),升高的LVEDP显著降低(P＜0.05,P＜0.01)。黄芩苷组血清CK和LDH含量分别是(72±19)kU·L~(-1),(64±15)kU·L~(-1)和(1 365±209)U·L~(-1),(1 124±169)U·L~(-1),均明显低于对照组[(90±23)U·L~(-1)和(1 826±123)U·L~(-1),P＜0.01]。对照组大鼠心肌SOD,Na~+-K~+-ATP酶和Ca~(2+)-ATP酶活性均明显低于假手术组,而降低的酶活性可被预先给予黄芩苷所升高(P＜0.05,P＜0.01)。此外,黄芩苷还可降低缺血心肌MDA含量,改善心肌超微结构。结论：黄芩苷通过清除氧自由基,抗脂质过氧化,改善心肌ATP酶活性而保护心肌缺血再灌注损伤。     

Reduction of myocardial infarct size by trapidil in anesthetized dogs

We studied the effect of trapidil on acute experimental myocardial infarction in anesthetized, openchest dogs. The size of myocardial infarction 8 h after ligation of the left anterior descending coronary artery was determined by planimetry of myocardial slices stained by the nitroblue tetrazolium method. Systemic hemodynamic variables, epicardial ST-segment elevation, activity of serum creatine phosphokinase (CPK), and changes of myocardial blood flow in the ischemic area were measured. Infusion of 3 mg/kg trapidil reduced the size of infarction and ameliorated the infarction-induced deterioration of systemic hemodynamic variables, such as the decrease in left ventricular dP/dt, aortic blood flow, and regional endomyocardial blood flow in the ischemic area. This dose of trapidil also suppressed ST elevation and significantly inhibited the increase in activity of serum CPK. Hyaluronidase also reduced the size of infarction significantly. These results suggest that trapidil alters the course of acute myocardial infarction favorably, presumably by increasing regional endomyocardial blood flow.     

Darbepoetin alfa protects the rat heart against infarction: dose-response, phase of action, and mechanisms

Erythropoietin is known to stimulate red cell production and has recently been shown to protect the heart against injury from ischemia/reperfusion. However, it is unknown whether darbepoetin alfa (Dpa), a long-acting analog of erythropoietin, can play a protective role against myocardial infarction. We assessed the potential protective role of Dpa in an in vivo rat model of myocardial ischemia/reperfusion and the underlying mechanisms. We found that a single intravenous Dpa treatment immediately before 30 minutes of regional ischemia reduced myocardial necrosis following 120 minutes of reperfusion in a dose-dependent manner. Optimal protection with Dpa against myocardial infarction was manifest at a dose of 2.5 microg/kg. Dpa conferred cardioprotection when administered after the onset of ischemia and at the start of reperfusion. Dpa (2.5 microg/kg) also reduced infarct size and Troponin I leakage 24 hours after reperfusion. Inhibition of p42/44 MAPK (PD98059), p38 MAPK (SB203580), mitochondrial ATP-dependent potassium (KATP) channels (5-HD), sarcolemmal KATP channels (HMR 1098), but not phosphatidylinositol-3 (PI3) kinase/Akt (Wortmannin and LY 294002) abolished Dpa-induced cardioprotection. Dpa confers immediate and sustained cardioprotection in rats, suggesting a potential therapeutic role of this long-acting erythropoietin analog for the treatment of acute myocardial infarction.     

The effects of disopyramide phosphate on early post-coronary artery ligation dysrhythmias and on epicardial ST-segment elevation in anaesthetized dogs.

1 The antidysrhythmic, haemodynamic and metabolic effects of intravenously administered disopyramide phosphate (1 to 5 mg/kg) have been studied in greyhounds, anaesthetized with trichloroethylene. 2 In doses of 2.5 and 5.0 mg/kg, disopyramide significantly reduced the ventricular dysrhythmias that occur in the initial 30-min period following acute coronary artery ligation. None of the disopyramide-treated animals developed ventricular fibrillations. 3 The metabolic consequences of coronary artery ligation, assessed by local coronary venous sampling from the ischaemic area, were not modified by disopyramide except that K+ egress was prevented. 4 There was evidence for substantial disopyramide-induced myocardial depression (decreased cardiac output and left ventricular dP/drmax with elevated ventricular filling pressure and pulmonary oedema and shunting) and it is suggested that great care be taken when the drug is administered intravenously in conditions where cardiac function is already compromised. Disopyramide also reduced myocardial blood flow. 5 In chloralose-anaesthetized mongrel dogs, disopyramide (2.5 mg/kg) significantly reduced the ST-segment elevation (assessed from epicardial recordings) that resulted from short (3 min) coronary artery occlusions. This could indicate a reduction in the extent and severity of myocardial injury or simply reflect decreased K+ efflux (since locally administered K+ itself increased ST-segment elevation).     

A characterization of myocardial infarction induced by thrombotic occlusion and a comparison with mechanical ligation of the rat coronary artery.

In the present study we examined two different methods for inducing myocardial infarction in rats. We previously developed an animal model of coronary artery thrombotic occlusion induced by a photochemical reaction, which occurs when rose bengal (a photosensitizer dye) is injected into the animal and is irradiated with green light. Arterial occlusion is thereby achieved nonmechanically. Using this method, we investigated the effect of thrombolytic intervention on myocardial infarct size. Infarct size was determined 24 h after the induction of myocardial infarction. When tisokinase (3 mg/kg), a native tissue-type plasminogen activator, was administered 3 min after the ST-segment elevation on a lead II electrocardiogram, the infarct size was 20.6 +/- 5.1%, which was significantly smaller than that of control rats (37.3 +/- 4.6%). When tisokinase was administered 10 min after the ST-segment elevation, the infarct size was 27.1 +/- 2.1%, which was not significantly smaller than that of controls. The rat coronary artery thrombosis model incorporates many aspects of coronary thrombosis. It differs from the coronary ligation model in that it lends itself to the study of thrombolytic agents on animal models of myocardial infarction.